As an air cleaner used for an internal combustion engine or the like, an air cleaner in which an air filter element having a cylindrical filter portion is installed to an air outlet (cylindrical member) projectingly formed in a casing to be contained in the casing is known. In this air filter element, both end surfaces of the hollow cylindrical filter portion are closed by end plates, and an opening for causing a fluid to pass through is formed in the center of at least one end plate, by which the air filter element is used by fitting the opening on the air outlet. Air is introduced from the outside of the casing into a space formed on the outside of the air filter element in the casing, caused to pass through from the outside to the inside in the cylindrical filter portion, and purified air is discharged from an inside space (filter chamber) of the air filter element to the outside of the casing through the air outlet.
Seal between the air filter element and the casing, which is necessary to prevent contaminated air from flowing into the filter chamber, is provided by the end surface of the end plate which is installed to the air outlet (end surface side of filter portion) and the inner surface of the casing opposed to the end plate (axial seal), by the opening of the end plate (inner periphery side of filter portion) and the outer surface of the air outlet (center seal (O-ring etc.)), or by both of them. U.S. Pat. No. 4,720,292 has disclosed an air filter using center seal.
An object of the present invention is to provide an air filter element having a novel seal construction (end plate construction) in which seal between an air filter element and a casing is provided between an opening of an end plate and the outer surface of an air outlet (cylindrical member), and a method of producing the air filter element.